Device for the drive control of a two-cylinder thick matter pump

ABSTRACT

A device for the drive control of a two-cylinder thick matter pump has a diverter which is arranged in a material charging container and a motor-driven hydraulic variable displacement pump, via which both the drive cylinders of the thick matter pump and the drive mechanism of the diverter are controlled. An adjusting throttle is arranged in a pressure line between the high-pressure outlet of the variable displacement pump and the drive cylinders of the thick matter pump. A control line which leads to an adjusting mechanism of the variable displacement pump is coupled back from the pressure line downstream of the adjusting throttle. A connecting line which leads to a supply connector of the diverter hydraulics and in which a fixedly adjusted throttle can be arranged is branched off from the pressure line upstream of the adjusting throttle.

The invention relates to a device for the drive control of a two-cylinder thick matter pump of the generic type specified in the preamble of patent claim 1.

Two-cylinder thick matter pumps of this type have two conveying cylinders which issue via end-face orifices into a material feed container and the conveying pistons of which can be actuated by means of hydraulically activated drive cylinders alternately in reciprocal motion so as to execute a filling stroke and a conveying stroke. Arranged inside the material feed container is a pipe switch which can be connected by means of a hydraulic drive mechanism alternately on the inlet side to the orifice of one of the conveying cylinders and which releases the orifice of the other conveying cylinder in each case, and which is connected on the outlet side to a conveying line for the thick substances to be conveyed. The thick matter pump has, furthermore, a motor-driven hydraulic variable displacement pump which has a suction inlet connected to a reservoir and a high-pressure outlet.

The drive cylinders for the conveying pistons can be connected alternately, in each case via a hydraulic connection located at one of their ends, by means of a first reversing valve to the high-pressure outlet of the variable displacement pump via a delivery line and to the reservoir via a return line. The drive cylinders are connected to one another at their other end via a rocking oil line. On the other hand, the hydraulic drive mechanism of the pipe switch has a cylinder arrangement activated on two sides, for example in the form of two series-connected plunger cylinders, the connections of which can be connected alternately via a second reversing valve to the delivery line leading to the high-pressure outlet of the hydraulic variable displacement pump and to the return line leading to the reservoir. To trigger follow-up control for the first and the second reversing valve, a central control is provided, which responds to end-of-travel signals of the passing drive pistons of at least one of the drive cylinders.

Thick matter conveyance and pipe switch reversal take place alternately in a single-circuit system via the same variable displacement pump which can be set continuously between zero conveyance and a stipulated maximum conveyance. The setting for thick matter conveyance depends upon a conveying quantity stipulated by the operator on a setting member and adapted to requirements, whereas, for reversing the pipe switch, the aim is to have a defined changeover time independently of the conveying quantity set in the machine. To set the conveying stream, the variable displacement pump has a conveying stream regulator, the control inlet of which is acted upon in the conveying phase by a variable control pressure adapted to the set conveying quantity, whereas, in the reversing phase, it is acted upon by a defined reversing pressure. The control inlet of the conveying stream regulator therefore has to be acted upon by different pressure control signals in the conveying phase and in the reversing phase, for which purpose a switchover valve (SOS valve) designed as a directional valve is used in the prior art. In other words, this means that the control signals for the conveying stream regulator appear on different control lines which are switched to the control inlet in the respective operating phases by means of a reversing valve.

One disadvantage of this type of control is that, to regulate the variable displacement pump, two control signals generated independently one another are used, for the appropriate choice of which during the conveying and reversing phase it is necessary to have an electromagnetically activated switchover valve. This requires considerable outlay both in terms of hardware and in control terms.

Proceeding from this, the object on which the invention is based is to improve the known device for the drive control of a thick matter pump to the effect that a simplification of the hydraulic switching arrangement can be achieved without any loss of functioning capacity.

To achieve this object, the feature combination specified in patent claim 1 is proposed. Advantageous refinements and developments of the invention may be gathered from the dependent claims.

The solution according to the invention is essentially that a setting throttle is arranged in the delivery line between the high-pressure outlet of the variable displacement pump and the first reversing valve, that a control line leading directly to an adjusting mechanism of the variable displacement pump is branched off from the delivery line downstream of the setting throttle, and that a connecting line leading to a supply connection of the second reversing valve is branched off from the delivery line upstream of the setting throttle, in which connecting line a permanently set throttle may be arranged, as required. A particular feature of the invention, therefore, is that the adjusting mechanism, containing a load-sensing regulator, of the variable displacement pump is activated only via one control line, and that the known switchover valve is therefore dispensed with. This is possible in that the variable displacement pump additionally comprises a pressure regulator for spilling the conveying quantity when a stipulated maximum pressure at the high-pressure outlet is exceeded. This maximum pressure is reached whenever, during the conveying operation, the drive pistons arrive at their limit stop and the pressure difference capable of being picked off at the setting throttle becomes zero. This is precisely the state in which the reversal of the pipe switch is initiated via the second reversing valve. In this case, the maximum pressure occurring at the high-pressure outlet of the variable displacement pump prevails at the fixed throttle and leads to a conveying stream, leading via the defined flow cross section of the connecting line, to the plunger cylinder acted upon at that moment by pressure. This conveying stream can be preset preferably via the flow cross section of a fixed throttle in the connecting line and via the maximum pressure such that pipe switch reversal takes place in a stipulated time of, for example, 200 ms. It holds from this that the variable displacement pump is conveying stream-regulated during the actual conveying operation, whereas, contrary to hitherto, in the reversing operation it is pressure-regulated via the stipulated maximum pressure.

In a further preferred refinement of the invention, the load-sensing hydraulics have a mechanically adjustable swashplate arranged in the variable displacement pump, as an adjusting member, and also a pressure balance which is connected to the swashplate and is spring-supported on the force side and to which the control line branched off downstream of the setting throttle is connected on the load side.

In order to ensure a fault-free change between the conveying phase and the reversing phase during the pumping operation of the two-cylinder thick matter pump, according to a preferred refinement of the invention it is proposed that the drive cylinders have at least two cylinder switching sensors which respond to the passing drive pistons and which are connected on the output side to signal inputs of the central control. By means of this measure, it is possible to trigger the reversing operation even some time before the drive piston comes to a stop at the cylinder end. This is necessary because the reversing operation via the reversing valves is possible only with a time delay. Thus, stop impacts of the drive pistons at the cylinder ends, which could lead to premature wear, can be avoided. The same also applies correspondingly to the reversal of the first reversing valve which should be triggered even before the plunger cylinders reach their end of travel during the reversal of the pipe switch. In order to make this possible, the drive mechanism of the pipe switch also has at least one pipe switch sensor which responds to the position, the speed or the ends of travel of the pipe switch and which is connected on the output side to a single input of the central control. In order to achieve all this, according to a further advantageous refinement of the invention, the reversing valves are designed as directional valves with electromagnetic pilot control members, the pilot control members of which are connected in each case to a control output of the central control.

The invention is explained in more detail below by means of an exemplary embodiment illustrated diagrammatically in the drawing in which:

FIG. 1 shows a detail of a two-cylinder thick matter pump in a partially sectional diagrammatic illustration;

FIG. 2 shows a circuit diagram of drive hydraulics for the two-cylinder thick matter pump.

The drive hydraulics illustrated in the hydraulic circuit diagram according to FIG. 2 are intended for a two-cylinder thick matter pump according to FIG. 1. The thick matter pump has two conveying cylinders 14, 14′, the end-face orifices 12, 12′ of which issue into a material feed container 10. The conveying pistons 16, 16′ of the thick matter pump can be actuated by means of hydraulically activated drive cylinders 18, 18′ alternately in reciprocal motion so as to execute a filling stroke (arrow 19′) and a conveying stroke (arrow 19″). Moveover, inside the material feed container 10 is located a pipe switch 22 which can be connected alternately on the inlet side by means of a hydraulic drive mechanism 24 to the orifice 12 of one of the conveying cylinders 14, while it releases the orifice 12′ of the other conveying cylinder 14′ in each case. The pipe switch 22 is connected on the outlet side to a conveying line 26. Moreover, a hydraulic variable displacement pump 28 driven by means of a motor 27 is provided, which has a suction inlet 32 connected to a pressureless reservoir 30 and a high-pressure outlet 36 connected to a delivery line 34.

The drive cylinders 18, 18′ can be connected alternately, in each case via a hydraulic connection 38, 38′ located at one of their ends, by means of a first reversing valve 40 designed as a 4/3-way valve to the high-pressure outlet 36 of the variable displacement pump 28 via the delivery line 34 and to the reservoir 30 via a return line 42. Moreover, the drive cylinders 18, 18′ are connected to one another at their other end via a rocking oil line 44.

The hydraulic drive mechanism 24 of the pipe switch 22 comprises two series-connected plunger cylinders 46 which can be connected alternately via a second reversing valve 48 to the delivery line 34 leading to the high-pressure outlet 36 of the hydraulic variable displacement pump 28 and to a return line 50 leading to the reservoir 30. Further, a central control 56 is provided, which responds to end-of-travel signals of the passing drive pistons 20, 20′ of at least one of the drive cylinders 18, 18′ and via which a follow-up control for the first and the second reversing valve 40, 48 can be triggered.

For controlling the conveying stream of the thick matter pump, a setting throttle 58, which is continuously adjustable by the operator, is arranged in the delivery line 34 between the high-pressure outlet 36 of the variable displacement pump 28 and the first reversing valve 40. A particular feature of the invention is that a control line 62 leading directly to an adjusting mechanism 60 of the variable displacement pump 28 is fed back from the delivery line 34 downstream (58′) of the setting throttle 58, and that a connecting line 66 leading to a supply connection 64 of the second reversing valve 48 is branched off from the delivery line 34 upstream (58″) of the setting throttle 58, in which connecting line a permanently set throttle 68 is arranged, as required.

The adjusting mechanism 60 comprises load-sensing hydraulics 70 which cause hydraulic power regulation in which both the pressure and the volume flow of the variable displacement pump 28 are adapted to the conditions required by the consumer. The pressure drop at the setting throttle 58 is used as the control variable.

In the exemplary embodiment shown, the load-sensing hydraulics 70 have a mechanically adjustable swashplate 72 arranged in the variable displacement pump 28, as an adjusting member, and also a pressure balance 73 which is connected to the swashplate 72 and is spring-supported on the force side and to which the control line 62 branched off downstream of the setting throttle 58 is connected on the load side. The variable displacement pump 28 can be adjusted continuously from zero conveying power to full conveyance.

In the zero position of the reversing valves 40, 48 designed as 4/3-way valves, with the exception of leakage oil losses, no hydraulic oil flows through the lines. At the same time, the variable displacement pump 28 maintains a standby pressure. If, then, by one of the reversing valves 40, 48 being opened, hydraulic fluid is conducted into the drives in the region of the drive cylinders 18, 18′ or in the region of the plunger cylinders 46, the conveying capacity of the variable displacement pump 28 is increased automatically. The variable displacement pump 28 in each case conveys only sufficient hydraulic fluid in order to maintain the currently required conveying pressure for the required conveying volume.

A particular feature of the invention is that the variable displacement pump 28 additionally comprises a pressure regulator, not illustrated, for spilling the conveying quantity when a stipulated maximum pressure is exceeded. This spill function is utilized in the activation of the drive mechanism 24 for the pipe switch 22.

It can be seen from FIG. 2 that the drive cylinders 18, 18′ have two cylinder switching sensors 52, 54 which respond to the passing drive pistons 20, 20′ and which are connected on the output side to signal inputs 52′, 54′ of the central control 56. Further, the drive mechanism 24 of the pipe switch 22 has a pipe switch sensor 74 which responds to the position, the speed or the ends of travel of the pipe switch and which is connected on the output side to a further signal input 74′ of the central control 56. The reversing valves 40, 48 are designed as directional valves with electromagnetic pilot control members 76, 78. The pilot control members are connected in each case to a control output 76′, 78′ of the central control 56. The activation signals for the reversing valves 40, 48 of the conveying piston drive and of the pipe switch drive are calculated from the signals coming from the cylinder switching sensors 52, 54 and, if appropriate, from the pipe switch sensor 74.

During the conveying phase, hydraulic oil flows from the variable displacement pump 28 via the delivery line 34, the setting throttle 58 and the reversing valve 40 into the drive cylinder 18, 18′ for the conveying piston 16, 16′ executing a conveying stroke 19″. Correspondingly, the oil quantity of the variable displacement pump 28 is set during the conveying phase via the load-sensing hydraulics 70 by setting a pressure drop at the setting throttle 58 via the control line 62. During the pipe switch movement, hydraulic oil flows via the connecting line 66 and the reversing valve 48 into the plunger cylinder 46 executing a delivery stroke. In this phase, the drive pistons 20, 20′ are at their limit stops, so that the maximum pressure occurs at the high-pressure outlet 36 of the variable displacement pump 28. The oil quantity passing through the connecting line 66 under the action of the maximum pressure is dimensioned such that the pipe switch 22 is reversed via the plunger cylinders 46 in a defined time of the order of 200 ms inside the material feed container 10. For this purpose, as required, a fixed throttle 68 may be arranged in the connecting line.

In summary, the following statement can be made: the invention relates to a device for the drive control of a two-cylinder thick matter pump with a pipe switch 22 arranged in a material feed container 10 and with a motor-driven hydraulic variable displacement pump 28, via which both the drive cylinders 18, 18′ of the thick matter pump and the drive mechanism 24 of the pipe switch are activated. A particular feature of the invention is that a setting throttle 58 is arranged in a delivery line 34 between the high-pressure outlet 36 of the variable displacement pump 28 and the drive cylinders 18, 18′ of the thick matter pump, that a control line 62 leading directly to an adjusting mechanism 60 of the variable displacement pump 28 is fed back from the delivery line 34 downstream of the setting throttle 58, and that a connecting line 66 leading to a supply connection 64 of the pipe switch hydraulics is branched off from the delivery line 34 upstream of the setting throttle 58, in which connecting line a permanently set throttle 68 may be arranged. What is achieved thereby is that the oil flow is conveying stream-regulated in the conveying phase, while it is pressure-regulated in the reversal phase. The latter is the case, above all, when the variable displacement pump 28 additionally comprises a pressure regulator for spilling the conveying quantity when a stipulated maximum pressure is exceeded.

LIST OF REFERENCE SYMBOLS

-   10 Material feed container -   12,12′ Orifices (conveying cylinders) -   14,14′ Conveying cylinder -   16,16′ Conveying piston -   18,18′ Drive cylinder -   19′ Filling stroke -   19″ Conveying stroke -   20,20′ Drive piston -   22 Pipe switch -   24 Drive mechanism -   26 Conveying line -   27 Motor -   28 Variable displacement pump -   30 Reservoir -   32 Suction inlet -   34 Delivery line -   36 High-pressure outlet -   38,38′ Hydraulic connection -   40 First reversing valve -   42 Return line -   44 Rocking oil line -   46 Plunger cylinder -   48 Second reversing valve -   50 Return line -   52, 54 Cylinder switching sensors -   52′,54′ End-of-travel signals -   56 Central control -   58 Setting throttle -   58′ Downstream -   58″ Upstream -   60 Adjusting mechanism -   62 Control line -   64 Supply connection -   66 Connecting line -   68 Throttle (permanently set) -   70 Load-sensing hydraulics -   72 Swashplate -   73 Pressure balance -   74 Pipe switch sensor -   74′ Signal input -   76,78 Pilot control members -   76′,78′ Control outputs 

1. A device for the drive control of a two-cylinder thick matter pump, with two conveying cylinders (14, 14′) which issue via end-face orifices into a material feed container (10) and the conveying pistons (16, 16′) of which can be actuated by means of hydraulically activated drive cylinders (18, 18′) alternately in reciprocal motion so as to execute a filling stroke (19′) and a conveying stroke (19″), with a pipe switch (22) which is arranged inside the material feed container (10), can be connected by means of a hydraulic drive mechanism (24) alternately on the inlet side to the orifice (12) of one of the conveying cylinders (14, 14′) and releases the orifice (12′) of the other conveying cylinder (14, 14′) in each case and which is connected on the outlet side to a conveying line (26), with a motor-driven hydraulic variable displacement pump (28) which has a suction inlet (32) connected to a pressureless reservoir (30) and a high-pressure outlet (36), the drive cylinders (18, 18′) being connectable alternately, in each case via a hydraulic connection (38, 38′) located at one of their ends, by means of a first reversing valve (40) to the high-pressure outlet (36) of the variable displacement pump (28) via a delivery line (34) and to the reservoir (30) via a return line (50), the drive cylinders (18, 18′) being connected to one another at their other end via a rocking oil line (44), the hydraulic drive mechanism (24) of the pipe switch (22) having a cylinder arrangement which is activated on two sides and the connections of which can be connected alternately via a second reversing valve (48) to the delivery line (34) leading to the high-pressure outlet (36) of the hydraulic variable displacement pump (28) and to the return line (50) leading to the reservoir (30), and with a central control (56), responding to end-of-travel signals of the passing drive pistons (20, 20′) of at least one of the drive cylinders (18, 18′), for triggering a follow-up control for the first and second reversing valve (48), wherein a setting throttle (58) is arranged in the delivery line (34) between the high-pressure outlet (36) of the variable displacement pump (28) and the first reversing valve (40), wherein a control line (62) leading directly to an adjusting mechanism (60) of the variable displacement pump (28) is fed back from the delivery line (34) downstream (58′) of the setting throttle (58), and wherein a connecting line (66) leading to a supply connection (64) of the second reversing valve (48) is branched off from the delivery line (34) upstream (58″) of the setting throttle (58).
 2. The device as claimed in claim 1, wherein a permanently set throttle (68) is arranged in the connecting line (66).
 3. The device as claimed in claim 1, wherein the cylinder arrangement activated on two sides comprises two series-connected plunger cylinders, the connections of which are connected to the second reversing valve.
 4. The device as claimed in claim 1, wherein the variable displacement pump (28) comprises a pressure regulator for spilling the conveying quantity when a stipulated maximum pressure is exceeded.
 5. The device as claimed in claim 1, wherein the adjusting mechanism (60) comprises load-sensing hydraulics (70) activated via the pressure drop at the setting throttle (58) as a control variable.
 6. The device as claimed in claim 5, wherein the load-sensing hydraulics (70) has a mechanically adjustable swashplate (72) arranged in the variable displacement pump (28), as an adjusting member, and also a pressure balance (73) which is connected to the swashplate (72) and is spring-supported on the force side and to which the control line (62) branched off downstream (58′) of the setting throttle (58) is connected on the load side.
 7. The device as claimed in claim 1, wherein the drive cylinders (18, 18′) have at least two cylinder switching sensors (52, 54) which respond to the passing drive pistons (20, 20′) and which are connected on the output side to signal inputs of the central control (56).
 8. The device as claimed in claim 1, wherein the drive mechanism (24) of the pipe switch (22) has at least one pipe switch sensor (74) which responds to the position, the speed or the ends of travel of the pipe switch (22) and which is connected on the output side to a further signal input of the central control (56).
 9. The device as claimed in claim 1, wherein the reversing valves (40, 48) are designed as directional valves with electromagnetic pilot control members (76, 78), the pilot control members (76, 78) of which are connected in each case to a control output (76′, 78′) of the central control (56). 